The present application proposes a theoretical interpretation of age differences in cognitive processes based on one of the best-documented empirical results in the psychological literature - a progressive decrease in speed of behavior with increasing age. Most if not all of this slowing-with-age phenomenon is determined by central rather than peripheral factors, and therefore it is likely to share causes with, and have consequences for, other cognitive processes. Unlike other theoretical speculations, the processing rate interpretation applies to a variety of cognitive activities ranging from simple reaction time, to memory, to decision-making. Furthermore, because of the central status of temporal variables in the perspective, there is greater opportunity for cross-disciplinary interaction and corroboration since time is as meaningful a measure in physiology as in psychology. Four broad approaches to age differences in processing rate and cognition will be pursued. One concerns a possible hypothesis (neural noise) about the cause of the slower processing rate in older adults. A second deals with the problem of which temporal measure is most satisfactory as an estimate of internal rate of information processing. The third issue involves the nature of the quantitative expression relating performance time to adult age. And finally, a fourth approach to the general problem will explore the consequences of slower rates of processing on a number of cognitive tasks such as memory and comprehension. It is believed that this broad, multifaceted perspective will not only lead to substantive advances in the knowledge about causes of age differences in cognition, but the methodological skills and sophistication of the principal investigator will also be increased because of the wide variety of procedures and techniques that are to be employed.